<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>

<body>

  <button>按钮</button>
  <script>

    const btn = document.querySelector('button')
    btn.addEventListener('click', function () {
      console.log('我被点击了')
      alert('点击了')
    })

  </script>

</body>

</html>